The epidemiology of multiple births

On the basis of MEDLINE and manual searches, we examined the main papers in the English literature regarding risk factors for spontaneous (i.e. not related to fertility drug use) multiple births. The constant frequency of monozygotic (MZ) pregnancies over time and in different geographical areas suggests that the determination of MZ twins is largely unchanged over time, and that a genetic mechanism may have a role. In contrast, temporal and geographical trends observed in dizygotic (DZ) pregnancies suggest that environmental factors play a role in determining this condition. At present, maternal age and hereditary components are the best-defined determinants for spontaneous multiple births.

Gestational trophoblastic tumours following initial diagnosis of partial hydatidiform mole

11 patients registered with an initial diagnosis of partial hydatidiform mole (PHM) subsequently required chemotherapy for a gestational trophoblastic tumour. In a retrospective review by histopathological examination and measurement of DNA ploidy, the diagnosis was confirmed as PHM in 5 cases and revised to complete hydatidiform mole in 4; in 2 cases there was no evidence of a molar pregnancy. 4 of the patients with PHM had no other known pregnancy before the gestational trophoblastic tumour and in 2 of these patients the tumour was diagnosed histologically as choriocarcinoma. Not all patients in whom PHM was diagnosed at referring hospitals proved to have the condition. Although the risk of a patient with PHM requiring chemotherapy for gestational trophoblastic tumour is of the order of 1 in 200, compared with 1 in 12 after a complete mole, there is no justification for excluding a patient from follow-up after the evacuation of a PHM.

Ovarian follicular development in cattle selected for twin ovulations and births12

Comparisons of numbers of antral ovarian follicles and corpora lutea (CL), of blood hormone concentrations, and of follicular fluid steroid concentrations and IGFBP activity were conducted between cows selected (twinner) and unselected (control) for twin births to elucidate genetic differences in the regulation of ovarian follicular development. Ovarian follicular development was synchronized among cows by a single i.m. injection of PGF2alpha on d 18 of the estrous cycle; six cows per population were slaughtered at 0, 24, 48, and 72 h after PGF2alpha. Jugular vein blood was collected from each animal at PGF2alpha injection and at 24-h intervals until slaughter. Ovaries of twinner cows contained more small (< or = 5 mm in diameter, P < 0.05), medium (5.1 to 9.9 mm, P < 0.05), and large (> or = 10.0 mm, P < 0.01) follicles and more (P < 0.01) CL than ovaries of controls. Follicular fluid concentrations of estradiol, androstenedione, testosterone, and progesterone reflected the stage of follicular development and were similar for twinner and control follicles at the same stage. Earlier initiation of follicular development and/or selection of twin-dominant follicles in some twinner cows resulted in greater concentrations of estradiol in plasma at 0, 24, and 48 h and of estradiol, androstenedione, and testosterone in follicular fluid of large follicles at 0 h after PGF2alpha for twinner vs. control cows (follicular status x time x population, P < 0.01). Binding activities of IGFBP-5 and -4 were absent or reduced (P < 0.01) in follicular fluid of developing medium and large estro-gen-active (estradiol:progesterone ratio > 1) follicles but increased with atresia. Only preovulatory Graafian follicles lacked IGFBP-2 binding, suggesting a possible role for IGFBP-2 in selection of the dominant follicle. Concentrations of IGF-I were twofold greater (P < 0.01), but GH (P = 0.10) and cholesterol (P < 0.05) were less in blood of twinners. Three generations of selection of cattle for twin ovulations and births enhanced ovarian follicular development as manifested by increased numbers of follicles within a follicular wave and subsequent selection of twin dominant follicles. Because gonadotropin secretion and ovarian steroidogenesis were similar for control and twinner cattle, enhanced follicular development in twinners may result from decreased inhibition by the dominant follicle(s), increased ovarian sensitivity to gonadotropins, and/or increased intragonadal stimulation, possibly by increased IGF-I.

Interleukin-4 and -10 gene polymorphisms and spontaneous preterm birth in multifetal gestations

OBJECTIVE

The purpose of this study was to determine the relationship between maternal and fetal carriage of different alleles of interleukin-4 and -10 genes and pregnancy outcome in multifetal gestations.

STUDY DESIGN

Buccal swabs from mother-infant pairs of 73 multifetal gestations were assayed for polymorphisms at position -590 of the interleukin-4 gene and position -1082 of the interleukin-10 gene. Pregnancy outcome data were obtained subsequently.

RESULTS

Spontaneous preterm birth occurred in 29 of the pregnancies (39.7%). A higher frequency of the interleukin-4 T allele was found among mothers with spontaneous preterm birth compared with mothers without spontaneous preterm birth (36.2% vs 18.2%; P=.02; odds ratio, 2.6; 95% CI, 1.1-5.9). Moreover, 20.7% of mothers who had spontaneous preterm birth were homozygous for the interleukin-4 T allele, as opposed to only 2.3% of mothers who did not have a spontaneous preterm birth (P=.01; odds ratio, 11.2; 95% CI, 1.2-69.5). Similarly, in 55.2% of the pregnancies that were complicated by spontaneous preterm birth, 2 fetuses carried the interleukin-4 T allele, compared with only 29.5% of the pregnancies that were not complicated by spontaneous preterm birth (p<.05; odds ratio, 2.9; 95% CI, 1.0-8.8). There was no relationship between mother and infant IL-10 genotype and spontaneous preterm birth.

CONCLUSION

Maternal and fetal carriage of the interleukin-4 T allele is associated with an increased risk of spontaneous preterm birth in multifetal gestations.

Genetic analysis prior to selective fetal reduction in multiple pregnancy: technical aspects and clinical outcome

Multiple pregnancies resulting from ovarian stimulation are at a higher risk of carrying at least one fetus affected by Mendelian or chromosomal anomalies, the incidence of which is directly related to the order of multiples. Genetic analysis before fetal reduction was offered to both high- and low-risk pregnant women carrying two or more fetuses after ovulation induction. Chorionic villus sampling (CVS) and fetal reduction were achieved by transabdominal needling. The use of short-term culture, the polymerase chain reaction and fresh tissue enzymatic analyses have made it possible for genetic diagnosis to be available in a few days. A total of 100 patients had multifetal pregnancy reduction performed by a single operator; all of them completed pregnancy and none was lost at follow-up. The total fetal loss before 24 weeks was 7% and no statistically significant relationship was found with the final number of fetuses and CVS. Perinatal losses (3.9%) were only present in the series with a final number of two fetuses. Pregnancy duration and birthweight were significantly higher in singletons than in twins, but were not related to CVS. The rate of chromosomal disorders was higher (7.2%) in the study series than in singleton pregnancies not undergoing fetal reduction. Diagnostic error due to incorrect sampling was reported in 1.5% of cases. These data support fetal reduction as a valuable strategy to improve the outcome of multiple pregnancy. The outcome of pregnancies reduced to singletons was significantly better than of those reduced to twins, and was not related to CVS.(ABSTRACT TRUNCATED AT 250 WORDS)

The endocrinology of dizygotic twinning in the human

Heredity, higher maternal age and increased parity are well defined conditions associated with dizygotic twinning. An endocrine model of excessive secretion of pituitary gonadotrophic hormones explains multiple ovulation as a result of multiple follicle growth. In hereditary conditions FSH levels are indeed clearly elevated because of increase in stimulating mechanisms that regulate pituitary gonadotropin secretion while in most non-hereditary conditions, overshoot FSH secretions occurs as a result of diminished ovarian feedback. Puberty is a condition in which the hypothalamic LHRH pulse generator is reinitiated and this is typically characterized by temporary overshoot LH and FSH secretion, probably due to not yet fully operational ovarian feedback. In adult females situations can be found that mimic this peripubertal event such as while recovering from hypothalamic amenorrhea. Under these circumstances more DZ twinning can be observed. Elevated FSH levels along with ageing in premenopausal women probably underlie the age related increased risk of dizygotic twinning. The apparent paradox in the combination of age related decline in fecundity and rise in twinning risk can be explained by incidental presence in the cohort of more than one follicle, containing vital oocytes under deficient feedback mechanisms that lead to high FSH.

Performance of cell-free DNA sequencing-based non-invasive prenatal testing: experience on 36,456 singleton and multiple pregnancies

BACKGROUND

This paper describes the clinical practice and performance of cell-free DNA sequencing-based non-invasive prenatal testing (NIPT) as a screening method for fetal trisomy 21, 18, and 13 (T21, T18, and T13) and sex chromosome aneuploidies (SCA) in a general Italian pregnancy population.

METHODS

The AMES-accredited laboratory offers NIPT in maternal blood as a screening test for fetal T21, T18, T13 and SCA. Samples were sequenced on a NextSeq 550 (Illumina) using the VeriSeq NIPT Solution v1 assay.

RESULTS

A retrospective analysis was performed on 36,456 consecutive maternal blood samples, including 35,650 singleton pregnancies, 800 twin pregnancies, and 6 triplet pregnancies. Samples were tested between April 2017 and September 2019. The cohort included 46% elevated-risk and 54% low-risk patients. A result indicative of a classic trisomy was found in 356 (1%) of singleton or twin samples: 254 T21, 69 T18, and 33 T13. In addition, 145 results (0.4%) were indicative of a SCA. Of the combined 501 screen-positive cases, 484 had confirmatory diagnostic testing. NIPT results were confirmed in 99.2% (247/249) of T21 cases, 91.2% (62/68) of T18 cases, 84.4% (27/32) of T13 cases, and 86.7% (117/135) of SCA cases. In the 35,955 cases reported as unaffected by a classic trisomy or SCA, no false negative cases were reported. Assuming that false negative results would be reported, the sensitivity of NIPT was 100.00% for T21 (95% Cl 98.47-100.0), T18 (95% Cl 94.17-100.0), and T13 (95% Cl 87.54-100.0). The specificities were 99.99% (95% Cl 99.98-100.0), 99.98% (95% Cl 99.96-100.0), 99.99% (95% Cl 99.97-100.0), and 99.95% (95% Cl 99.92-99.97) for T21, T18, T13, and SCA, respectively.

CONCLUSION

This retrospective analysis of a large cohort of consecutive patients who had whole-genome sequencing-based NIPT for classic trisomies and SCA shows excellent detection rates and low false positive rates.

Beta-thalassemia syndromes and pregnancy

The literature relating to homozygous beta-thalassemia and the problems these patients have during their pregnancy is reviewed and another case report of a twin pregnancy in a homozygous beta-thalassemia individual is included. The majority of cases described refer to the intermedia clinical form of the hematological problem because patients with thalassemia major generally have poor sexual development. Although the reported cases had a greater frequency of delayed development, only one woman suffered from infertility and required ovulation induction agents. The thalassemia pregnant mother faces deleterious consequences resulting from chronic anemia and in nonsplenectomized patients there remains the risk of the onset of a hypersplenic crisis. The problems of splenectomized patients during pregnancy is also discussed. The chronic anemia of thalassemic patients predisposes to a poor fetal outcome with greater fetal loss, preterm labor, and intrauterine growth retardation.

Single uterine entry for genetic amniocentesis in twin pregnancies

In 176 diamniotic twin pregnancies at 10-20 weeks of gestation, amniotic fluid for cytogenetic studies was successfully obtained from both sacs by the use of a single uterine entry. There were no cases of discordancy between sex at amniocentesis and birth. There were six pregnancies with fetal unbalanced chromosomal defects; in one pregnancy both fetuses were abnormal and in five pregnancies only one fetus was abnormal. The total fetal loss rate was 5.7% (20 of 352 fetuses), including six (1.7%) terminations or selective fetocides and 14 (4.0%) spontaneous deaths. In the 176 pregnancies there were five (2.8%) with no survivors, including one termination and four (2.3%) spontaneous miscarriages or intrauterine deaths. There are only two (1.1%) pregnancies in which amniocentesis could have contributed directly to the losses and therefore the procedure-related rate of fetal loss may be similar to that in singleton pregnancies. The median gestation at delivery was 37 (range 16-40) weeks and delivery before 32 weeks occurred in 9% of the pregnancies. The birth weight distribution was similar to that reported in singleton pregnancies. This study demonstrates that in twin pregnancies amniotic fluid for cytogenetic studies can be obtained successfully from both sacs by use of a single uterine entry. The risk of fetal loss from this procedure appears to be similar to that in singleton pregnancies.

Genetic diagnosis in multiple pregnancies

A twin gestation presents unique problems in both genetic counseling and prenatal diagnosis. This article describes the specific genetic counseling concerns for a twin gestation and outlines the available techniques for genetic prenatal diagnosis. The technical aspects, risks and benefits to the pregnancy of amniocentesis and of chorionic villi sampling are compared. Although the risk of miscarriage after amniocentesis in a twin gestation is at least double that for a singleton, much of this additional risk is secondary to the inherent hazards of twins and not procedure-related. In experienced centers, chorionic villi sampling is equally safe and efficacious, and allows an earlier diagnosis that may be beneficial when discordant results are found. The aspects of serum screening unique to twin gestations are also outlined. Prenatal diagnosis by both chorionic villus sampling and amniocentesis can be safely performed in twin gestations and higher-order multiple gestations. Serum screening is also useful, but appears to have a lower sensitivity and specificity than in singletons.

Associations between siblings for esotropia and exotropia

OBJECTIVE

To quantify familial aggregation of esotropia and exotropia in children examined in a large multicenter study.

METHODS

Pregnant women and their children were examined in the Collaborative Perinatal Project of the National Institute of Neurological Disorders and Stroke, Bethesda, Md. Strabismus was evaluated in the children during follow-up examinations up to the age of 7 years. The second-order generalized estimating equations approach to logistic regression was used to estimate familial aggregation of esotropia and exotropia.

RESULTS

For any pair of siblings, the odds for one sibling having esotropia more than doubled when the other sibling had esotropia. For exotropia, there were differences in sibling associations based on birth relationships. In particular, there was no statistically significant association between siblings from separate single births. On the other hand, for the pairs of siblings from multiple births (ie, twins, triplets, and quadruplets), the odds for exotropia in one sibling were increased by at least a factor of 17 when the other sibling from that birth also had exotropia. For both esotropia and exotropia, adjustment for previously identified risk factors only somewhat reduced the magnitudes of the observed associations. Limited data on zygosity showed a stronger association between monozygotic twins than between dizygotic twins.

CONCLUSIONS

There is a significant familial component in the cause of strabismus. Furthermore, there are important contributions to this familial aggregation beyond those associated with known risk factors for strabismus.

Genetic amniocentesis in multiple pregnancy

OBJECTIVES

Second-trimester genetic amniocentesis is the most frequently used invasive prenatal diagnostic technique. Several reports have been published about the effect of genetic amniocentesis on fetal loss in multiple pregnancies over the past two decades. Here we analyze our experience with genetic amniocentesis in multiple pregnancies over the past 10 years.

METHODS

Details of 184 multiple pregnancies were processed in all cases in whom genetic amniocentesis was performed in women who presented at our department since 1990. The outcomes of 175 cases (95.1%) out of 184 genetic amniocenteses were available to us. As a control group, we followed up the outcome of 300 twin pregnancies in which no genetic amniocenteses were performed.

RESULTS

We found that the proportion of spontaneous losses in multiple pregnancies between the 18th and the 24th gestational weeks was 2.39%, whereas if genetic amniocentesis was performed the loss rate before the 24th week was 3.87%. The perinatal mortality rate was 10.03/1,000 in the group who underwent amniocentesis, while it was 10.52/1,000 in the group without amniocentesis.

CONCLUSIONS

Our results suggest that the genetic amniocentesis performed in multiple pregnancies slightly increased (1.48%) the fetal loss rate until the 24th week. Beyond 5 weeks after the procedure, no consequent fetal loss should be expected. In our study the intervention did not have any undesired effect on perinatal mortality rates.

Association of a single nucleotide polymorphism in SPP1 with growth traits and twinning in a cattle population selected for twinning rate

Continued validation of genetic markers for economically important traits is crucial to establishing marker-assisted selection as a tool in the cattle industry. The objective of the current study was to evaluate the association of a SNP (T(9)/T(10)) in the osteopontin gene (SPP1) with growth rate in a large cattle population spanning multiple generations and representing alleles from 12 founding breeds. This population has been maintained at the US Meat Animal Research Center since 1981 and subjected to selection for twinning rate. Phenotypic records for this population included twinning rate and ovulation rate, providing an opportunity to examine the potential effects of SPP1 genotype on reproductive traits. A set of 2,701 animals was geno-typed for the T(9)/T(10) polymorphism at SPP1. The geno-typic data, including previously genotyped markers on chromosome 6 (BTA6), were used in conjunction with pedigree information to estimate genotypic probabilities for all 14,714 animals with phenotypic records. The genotypic probabilities for females were used to calculate independent variables for regressions of additive, dominance, and imprinting effects. Genotypic regressions were fit as fixed effects in a mixed model analysis, in which each trait was analyzed in a 2-trait model where single births were treated as a separate trait from twin births. The association of the SPP1 marker with birth weight (P < 0.006), weaning weight (P < 0.007), and yearling weight (P < 0.003) was consistent with the previously reported effects of SPP1 genotype on yearling weight. Our data supports the conclusion that the SNP successfully tracks functional alleles affecting growth in cattle. The previously undetected effect of the SNP on birth and weaning weight suggests this particular SPP1 marker may explain a portion of the phenotypic variance explained by QTL for birth and HCW on BTA6.

Excessive follicular recruitment and growth in mothers of spontaneous dizygotic twins

We wished to establish the frequency, regularity and laterality of multiple ovulation in mothers of dizygotic (DZ) twins and controls. Subjects had regular menses and were not using oral contraceptives. Ovarian ultrasound scans were taken over a number of cycles in 21 mothers of DZ twins and 18 controls (including 13 mothers of monozygotic [MZ] twins). Multiple large follicles (greater than or equal to 12 mm diameter) were seen significantly more frequently in mothers of DZ twins (13/21 mothers, 24/77 cycles, average +/- SE follicles/cycle 1.34 +/- 0.11) than controls (2/18 mothers, 3/31 cycles, average 1.10 +/- 0.08). Both ipsilateral and contralateral multiple follicles were observed. In one case a mother of DZ twins showed multiple large follicles in 7 out of 10 cycles in which she was scanned, including both ipsi- and contralateral patterns of occurrence.

The number of dichorionic twin pregnancies is reduced by the common MTHFR 677C-->T mutation

In multiple pregnancies, demands for folic acid are considerably increased. The most common inborn error of folate metabolism is mild methylenetetrahydrofolate reductase (MTHFR) deficiency due to the synthesis of a thermolabile variant of the enzyme with impaired catalytic activity which leads to reduced 5-methyltetrahydrofolate (5-methyl-THF) and mildly elevated homocysteine plasma concentrations when folate status is inadequate. To investigate whether the number of offspring is influenced by this mutation, we determined the frequency of the 677C-->T substitution in 156 singleton and 40 twin mothers with dichorionic placentation. The T allele frequency in singleton (0.30) and twin mothers (0.16) was significantly different (P = 0.011). Mothers with the 677C-->T mutation had a 2.28 times lower risk of having a twin pregnancy than those without (95% confidence interval = 1.18-4.66; P = 0.008). Our observation would explain, at least in part, the hereditary trait of multiple gestations and is in agreement with the ethnic distribution pattern of the T allele which has been found to be inversely correlated with the incidence of dichorionic twins. Our findings suggest that the MTHFR 677C-->T mutation interferes with human brood size, probably by influencing the proliferation of rapidly dividing embryonic and maternal cells.

Genetic control of multiple births in low ovulating mammalian species

In mammals, litter size is a highly variable trait. Some species such as humans or cattle are monotocous, with one or sometimes two newborns per birth, whereas others, the polytocous species such as mice or pigs, are highly prolific and often produce a dozen newborns at each farrowing. In monotocous species, however, two or three newborns per birth may sometime be unwanted. In more polytocous species such as sheep or pigs, litter size is studied in order to increase livestock prolificacy. By contrast, twinning rates in humans or cattle may increase birth difficulties and health problems in the newborns. In this context, the aim of our review was to provide a clearer understanding of the genetic and physiological factors that control multiple births in low-ovulating mammalian species, with particular focus on three species: sheep, cattle, and humans, where knowledge of the ovulation rate in one may enlighten findings in the others. This article therefore reviews the phenotypic and genetic variability observed with respect to ovulation and twinning rates. It then presents the QTL and major genes that have been identified in each species. Finally, we draw a picture of the diversity of the physiological mechanisms underlying multiple ovulation. Although several major genes have been discovered in sheep, QTL detection methods in humans or cattle have suggested that the determinism of litter size is complex and probably involves several genes in order to explain variations in the number of ovulations.

Fetal aberrant right subclavian artery (ARSA) - a potential new soft marker in the genetic scan?

PURPOSE

The aim of this study was to evaluate the prevalence of an aberrant right subclavian artery (ARSA) in a mixed-risk population in the second trimester and to assess its potential as a new soft marker in the genetic scan.

MATERIALS AND METHODS

Fetal echocardiography was performed prospectively in 1337 fetuses at 16 - 28 weeks of gestation during a 12-month period at two referral centers for prenatal diagnosis. The presence of ARSA was verified by visualization of the transverse 3-vessel trachea view with color Doppler sonography.

RESULTS

The total rate of fetuses with an ARSA was 1.05 % (14 / 1337). The spectrum of associated findings in affected fetuses included: one trisomy 21, one unbalanced inversion of chromosome 9, one triploidy and two non-chromosomally related structural defects. Nine fetuses had no anomalies. The calculated odds ratio for the presence of an ARSA in the case of Down syndrome compared with healthy fetuses was 12.6 (95 % CI, 1.93 - 86.10).

CONCLUSION

The presence of an ARSA is more common in fetuses with trisomy 21 and other chromosomal defects than in healthy fetuses. Although it can be considered as a weak marker, the second trimester diagnosis of an ARSA should prompt a detailed search for additional "soft markers" and structural defects.

A sex-specific test of selection in utero

We find support for the hypothesis that changes in the monthly odds of a twin among live-born males predict subsequent and opposite changes in the odds of a twin among live-born females. The hypothesis arises from the long standing argument that natural selection has conserved mechanisms by which pregnant women in stressed populations spontaneously abort fetuses least likely to yield grandchildren. Previous attempts to empirically test this argument focus almost entirely on males. We contribute to the literature by showing that, consistent with the logic of natural selection, maternal adaptations to environmental changes likely have effects on the survival of both male and female conceptuses and fetuses.

Genetic differentiation of complete hydatidiform moles coexisting with normal fetuses by short tandem repeat-derived deoxyribonucleic acid polymorphism analysis

OBJECTIVE

We applied deoxyribonucleic acid polymorphism analysis on the basis of differences in the number of short tandem repeat sequences to genetically differentiate dizygotic twins with complete hydatidiform moles and normal fetuses from partial moles presenting a similar appearance.

STUDY DESIGN

Six pregnant women exhibiting apparent moles and coexisting fetuses were the subjects of this study. Eight polymorphic loci including short tandem repeat sequences were amplified by polymerase chain reaction from deoxyribonucleic acid of peripheral leukocytes of parents, umbilical cord, grossly normal placenta-villi, and molar tissue. The segregation of alleles among samples were determined by comparing band patterns on polyacrylamide gels.

RESULTS

In all 6 cases amplifications of polymorphic loci provided sufficient information to determine the parental origin. At informative loci the alleles of cord and placenta-villi were transmitted from both patients and husbands whereas molar tissue had only paternal alleles. These allele segregations indicated 2 different genetic origins, namely, normal parental for a fetus and androgenetic for molar tissue, and thus the diagnosis of dizygotic twins with a complete hydatidiform mole and a normal fetus was made. Additionally, the molar component was defined as a heterozygous mole in 2 cases.

CONCLUSION

Short tandem repeat-derived deoxyribonucleic acid polymorphism analysis was demonstrated to be a useful and precise procedure for the differential diagnosis of a complete hydatidiform coexisting with a normal fetus and the determination of its zygosity as well.

Fusion as the Etiology of Chimerism in Monochorionic Dizygotic Twins

In a dizygotic pregnancy within monochorionic placenta, findings consistent with chimerism were detected. Monochorionicity was confirmed by a combination of ultrasound, histological evaluation and DNA technology. Etiologic hypotheses are offered to explain this rare circumstance.

Embryo number and periconceptional undernutrition in the sheep have differential effects on adrenal epigenotype, growth, and development

Exposure to poor maternal nutrition around the time of conception results in an early prepartum activation of the fetal pituitary-adrenal axis and in increased adrenal growth and stress response after birth associated with epigenetic changes in a differentially methylated region (DMR) of adrenal IGF2/H19. We have determined the effects of maternal undernutrition during the periconceptional period (PCUN: 70% of control intake from 60 days before until 6 days after conception) and early preimplantation period (PIUN: 70% of control intake for 6 days after conception) on fetal plasma ACTH and cortisol concentrations and fetal adrenal ACTHR, StAR, 3βHSD, CYP11B, CYP17, TGFβ1, IGF1, IGF1R, IGF2, and IGF2R mRNA expression and the methylation level of sites within the DMRs of IGF2/H19 and IGF2R in the adrenal of twin and singleton fetuses at 136-138 days gestation. Being a twin resulted in a delayed prepartum increase in fetal ACTH and in a lower cortisol response to CRH in the control but not PCUN and PIUN groups. PCUN, but not PIUN, resulted in an increase in adrenal weight and CYP17 expression in singletons, a decrease in adrenal IGF2 expression in singletons, and an increase in adrenal IGF2R expression in both twins and singletons. IGF2/H19 and IGF2R DMR methylation levels and ACTHR expression were lower in the twin adrenal. Thus, exposure of the oocyte and embryo to maternal undernutrition or to the environment of a twin pregnancy have differential effects on epigenetic and other factors that regulate fetal adrenal growth and IGF2 and IGF2R expression.

Mutations in the follicle-stimulating hormone receptor and familial dizygotic twinning

Concentrations of follicle-stimulating hormone (FSH) have an important role in multiple ovulation. An association has been reported between mutations in the FSH receptor (FSHR) in a family with increased twinning frequency. We sequenced the transmembrane region of FSHR (located on chromosome 2) in 21 unrelated mothers of dizygotic twins and found no differences to the published sequence. A linkage study of 183 sister pairs and trios, in which all sisters had given birth to spontaneous dizygotic twins, excluded linkage to this region of chromosome 2. We conclude that mutations in FSHR are not a common cause of familial dizygotic twinning.

Association of a maternal CD14 -159 gene polymorphism with preterm premature rupture of membranes and spontaneous preterm birth in multi-fetal pregnancies

CD14, the major receptor for bacterial lipopolysaccharide (LPS) as well as other microbial antigens, is a component of the innate immune system. We hypothesized that a single nucleotide C>T polymorphism at position -159 in the CD14 gene that results in elevated CD14 production would influence susceptibility to preterm premature rupture of membranes (PPROM) and spontaneous preterm birth (SPTB) in multi-fetal pregnancies. DNA from 107 mother-twin and three mother-triplet pairs was analyzed. Pregnancy outcomes were obtained after completion of testing. CD14*T homozygosity was present in 39.3% of 28 women whose pregnancies ended with PPROM, as opposed to 18.1% of 72 pregnancies without a SPTB (P=0.03). There was no relation between the fetal CD14 genotype and PPROM. The likelihood ratio (LR) for PPROM was 2.2 for women homozygous for CD14*T. The LR increased to 3.3 and 3.6 if the CD14 polymorphism was present in combination with previously determined maternal polymorphisms in the genes coding for the inducible 70kDa heat shock protein (hsp70-2) and the interleukin-1 receptor antagonist (IL1RN), respectively. Thus, an enhanced maternal pro-inflammatory immune response to LPS may increase susceptibility to PPROM in multi-fetal pregnancies.