Prenatal Smoking in Two Consecutive Pregnancies: Georgia, 1989–1992

Objective: To explore the patterns of prenatal smoking among women whose first and second pregnancies ended in live births. Methods: We used population-based data to explore prenatal smoking among 14,732 white and 8968 black Georgia residents whose first and second pregnancies ended in live births during 1989–1992. Smoking status was obtained from birth certificates linked for individual mothers. Because of demographic differences, we analyzed white and black women separately. Results: Approximately 15% (2253) of white women and 4% (318) of black women smoked during their first pregnancy. Of those smokers, 69% (1551) of white women and 58% (184) of black women also smoked during their second pregnancy. For both white and black nonsmokers during the first pregnancy, low education was the most significant predictor of smoking during the second pregnancy, after adjusting for consistency of the father's name on the birth certificate, prenatal care, birth interval, mother's county of residence, and birth outcome. Conclusions: The prevalence of smoking in this study may be low because of underreporting of prenatal smoking on birth certificates. The majority of women who smoked during their first pregnancy also smoked during their second, suggesting that these women exposed their first infant to tobacco smoke both in utero and after delivery. Practitioners should offer smoking cessation programs to women during, as well as after, pregnancy. Pediatricians should educate parents on the health risks to young children of exposure to environmental tobacco smoke and refer smoking parents to smoking cessation programs.     

Interpregnancy Interval and Risk of Adverse Pregnancy Outcomes: A Register-Based Study of 328,577 Pregnancies in Denmark 1994–2010

Objectives To investigate the associations of interpregnancy interval (IPI) with miscarriage, stillbirth, preterm delivery and small for gestational age delivery. Methods The study population comprised all women who had a live birth and at least one subsequent pregnancy in Denmark during the period from 1994 to 2010 (N?=?328,577). Linear regression was used to estimate risk differences for miscarriage, stillbirth, preterm delivery and small for gestational age delivery according to IPI. Results The results were heterogeneous: the risk of miscarriage increased monotonically with the length of the IPI. Compared to women with IPIs of 18–23 months, women with IPIs of 0–5 months experienced 18.7 (13.1–24.2) fewer miscarriages per 1000 pregnancies, while women with IPIs of ≥?60 months experienced 28.7 (23.4–34.0) more miscarriages per 1000 pregnancies. We found that women with IPIs of ≥?60 months had 1.7 (0.4–3.0) more stillbirths per 1000 births compared to women with IPIs of 18–23 months. U-shaped associations were seen for preterm delivery and small for gestational age delivery with women with IPIs of 18–23 months experiencing the lowest risks of these outcomes. Conclusions for Practice The heterogeneity in associations between IPI and adverse pregnancy outcomes suggests that different mechanisms of action may be at play at various times in the antepartum period. While the finding for miscarriage suggests that fecundity is an important determinant for IPI, the findings for preterm delivery and small for gestational age delivery suggest the coexistence of the maternal depletion syndrome mechanism and the physiological regression mechanism and the finding for stillbirth speaks against a strict maternal depletion syndrome explanation.     

Concordance Rates of Birth Defects After Assisted Reproductive Technology Among 17 258 Japanese Twin Pregnancies: A Nationwide Survey, 2004–2009

Background

Most twins after assisted reproductive technology (ART) are dizygotic. Analysis of dizygotic twin pairs is useful in assessing familial aggregation in the development of birth defects.

Methods

Using nationwide post-ART data from the Japan Society of Obstetrics and Gynecology, recurrence risk ratios (RRRs)—defined as probandwise concordance rates of birth defects in twins divided by the prevalence of birth defects in the general population—were calculated as indicators of familial aggregation. Birth defects were then reclassified according to the ICD-10 categories corresponding to codes Q00–Q99. From 2004 to 2009, there were 17 258 twin pregnancies.

Results

At least 1 birth defect was noted in 236 twin pairs: 11 concordant and 225 discordant pairs. Regarding major organ systems, high probandwise concordance rates were observed for congenital malformations of eye, ear, face, and neck (11.8%), cleft lip and cleft palate (10.5%), congenital malformations of the nervous system (9.8%), and other congenital malformations of the digestive system (9.5%). High RRRs were observed for congenital malformations of eye, ear, face, and neck (RRR = 233), specifically other congenital malformations of the ear (RRR = 449); congenital malformations of the great arteries (RRR = 235), specifically those of the patent ductus arteriosus (RRR = 530); and for cleft lip and cleft palate (RRR = 208), specifically cleft palate with cleft lip (RRR = 609). The probandwise concordance rate of any birth defect (8.9%) was nearly identical to the approximated recurrence risk of sib-pairs (8.8%), which assumed multifactorial inheritance.

Conclusions

The present findings suggest that familial aggregation is a factor in some birth defects.Key words: birth defects, assisted reproductive technology (ART), twin pairs, concordance rate, nationwide epidemiologic study