Abstract
Introduction
Advances in ultrasound technology have allowed sex determination to be offered to prospective parents during the anomaly scan visit in ultrasound departments. There has been much publicity recently with respect to terminations having been requested based on fetal sex. In other countries there are skewed male to female birth ratios due to ‘wrong sex’ termination, which is usually female. This study has been designed to determine the prevalence of women requesting sex identification and the accuracy of sex determination. Additionally, we have identified demographic and clinical factors, which may be associated with this decision.
Methods
Ethical approval was obtained from the North West Proportionate Review Board. The study included all 2780 women attending their anomaly scan at Salford Royal Hospital in 2009. From their medical records we have determined how many women requested sex identification, the sex that was predicted and the accuracy of this prediction. We also recorded the women's age, parity, race, religion, and past history of fertility problems.
Results
The results showed that 74% of women wanted to know the sex of their baby, of whom 1.8% were unable to be told because of the position of the fetus at the time of the scan. Sex determination was correct in 99.4% of cases and there was no significant difference between the identification of males and females. Factors that were significantly associated with an increased desire to know were, being younger ( < 30 years); multiparous; of Afro Caribbean, Eastern European or Chinese origin [chi squared < 0.05]. Jewish women were the group least likely to request the information (32%), along with women aged 41–47 with fertility problems (42%).
Conclusion
The prevalence, sensitivity and accuracy of ultrasound sex determination have been established in this study and subgroups identified that request this information.
Introduction
Ultrasound scans were introduced to obstetric medicine in the late 1950s by Professor Ian Donald and his team based in Glasgow. 1 Fetal sex determination by ultrasound was first documented in 1977 by Stocker and Evens. 2 However, it has only been with advances in the quality of scans over the past 30 years that the accuracy of sex determination has improved to a standard where it is now commonly offered during the anomaly scan visit. Although sexing is not part of the NHS fetal anomaly screening programme, it is still offered commonly by many hospitals. Indeed at Salford Royal Foundation Trust (SRFT) Hospital it has been routinely offered since 2007. On the basis of previous published studies it is extremely variable how many women choose to be told the sex of their unborn child. Percentages quoted range from 58%–94.5%. 3–5 The difference in prevalence of fetal sex determination seems to be influenced by several demographic factors including ethnic origin, and religious beliefs. This study aims to determine what percentage of women wish to be told the sex, and how accurate transabdominal ultrasound sex determination is at SRFT Hospital. There has been much publicity recently with respect to terminations having been at least requested based on fetal sex and the Care Quality Commission has just completed an inspection which has highlighted major irregularities in the application of the 1967 Abortion Act in some clinics. In addition, other countries, such as China, have skewed male to female birth ratios which are believed to be due to terminations for ‘wrong sex’ pregnancies, usually of female fetuses.
Fetal sex can be determined by different techniques depending on the gestation of the pregnancy. Fetal sex determination should not be attempted until the pregnancy is beyond 12 weeks; prior to this the percentage error is significantly higher. 6,7 Fetal sex assessment between approximately 12–24 weeks can be assessed using the ‘Sagittal Sign’. This technique was first described by Emerson et al. 1989 and refers to the positioning of the genital tubercle when viewed in the sagittal plane. In males the penis points up (cranial position), whereas in females the clitoris points down (caudal position). This study found that the sex was described accurately in 98% at 18 weeks and 100% at 20.4 weeks. 8 Bronshtein et al. described another way to identify a male fetus using the ‘Dome Sign’, which involves visualising the scrotum as a dome at the base of the penis. In addition, they noted that females should be determined by finding the labia majora and minora which at this stage are seen as two or four parallel lines. 9 Beyond 24 weeks the fetal sex is determined by seeing the developed external genitalia. For males this involves visualising the penis and scrotum and for females the labia majora and minora. When determining female sex it is imperative this process is not centred on the absence of male genitalia but instead on the presence of female genitalia. 6
One difficulty with the use of ultrasound to determine fetal sex is in cases where there is ambiguous genitalia. Pajkrt and Chitty explain how the identification of circulating fetal male DNA in maternal plasma can provide an alternative to invasive prenatal karyotyping. 10 In cases where there is an increased risk of serious sex linked diseases, several studies have shown that the concurrent use of ultrasound and identification of fetal male DNA in maternal plasma is accurate for sex identification. 10
Different studies have noted varying accuracy of sex prediction using trans-abdominal ultrasound, ranging from 86%–100% accuracy. 5–7,11–13 The differences in accuracy may be a reflection of the quality of the ultrasound equipment or of the sonographers' training and experience in sex determination.
The decision to find out the sex of the unborn child may be affected by numerous factors. Previous studies have used questionnaires to determine why expectant mothers made their decision. These encompassed demographic, clinical, social and psychological factors. Between the studies different results have been obtained, but most have confirmed that younger mothers were more likely to want to know the sex. In addition, future child bearing and housing plans were consistent reasons for wanting to know the sex. 3,5,14,15
This study aims to investigate the accuracy of fetal sex determination at SRFT hospital and the factors which influence the women's decision.
Aims and methods
For this study ethical approval was sought and approved by the North West Proportionate Review Board (approval reference number:11/NW/0433). This was a retrospective cohort study of all women who attended their anomaly scan and gave birth at SRFT Hospital during 2009. This study has been designed to determine the percentage of women who wanted to know the sex of their unborn child at the time of their anomaly scan (18–20 weeks); in addition, to establish the accuracy of sex prediction and whether there were any factors which influenced the mother's decision, including their age, race, religion, parity and previous history of fertility problems. The cohort was obtained using the 2009 birth register at SRFT hospital. We then documented their demographic details anonymously. The data required was obtained using the electronic patient record system at Salford Royal Hospital. This system was also used to locate the ultrasound scan report which documents whether the mother chose to be told the sex of the baby, and if so, the predicted sex. By checking delivery details we could determine the accuracy of the prediction at the time of the anomaly scan.
Results and discussion
Did women want to know the sex of their unborn child?
This study has shown that of the 2780 women who attended their ultrasound scans and gave birth at SRFT Hospital, 2064 (74.2%) women wanted to know the sex and 716 (25.8%) did not want to be told. This is in comparison to earlier studies which have suggested a prevalence of between 58%–95% of women wanting to know the sex of their baby; however these studies involved smaller numbers. 3–5
Only 38 women (1.8%) could not be told the sex due to fetal lie. This small percentage compares favourably with other studies. Meagher and Davison 12 noted sexing was not possible in 8.7% of their sample, and a study by Harrington et al that included an imposed time limit for sex determination found the sex to be inconclusive in 6.8%. 5
The reasons why such a high percentage of women want the sex determined is multifactorial. Reasons may include wanting to be prepared for the baby's arrival, for example decorating the nursery, buying clothes and picking names. There may also be social factors that lead to this decision such as housing arrangements and future children. 3,14 Sex determination will be particularly important for women with a family history of sex linked abnormalities. 10,16
How accurate was sex determination using ultrasound?
Of the 2026 women in whom sex identification was possible there were 13 women told the incorrect sex. Therefore, ultrasound sex determination in 2009 at SRFT Hospital had an accuracy of 99.4%. Some mothers may have been told the incorrect sex as a result of the baby having anatomical anomalies as discussed by Pajkrt and Chitty. 10 For this study it was not documented if any of the wrongly identified babies had ambiguous genitalia. However, having a child with ambiguous sex at delivery after being told a ‘definitive’ sex prenatally will make the coping process all the more difficult. Another reason why women may have been told the wrong sex could be related to maternal obesity, which will make the scanning process more challenging and give poorer definition. Of the 13 women told the incorrect sex, 5 were said to have an ‘increased body habitus’ on the scan report. A further reason for the inaccuracy may be due to sonographer error. The 13 incorrect sex predictions were made by eight different members of staff, six mistakes by one sonographer and the other seven mistakes were made by seven different sonographers. The sonographer who was incorrect on six occasions identified all the babies as female when they were in fact male. In terms of the specificity for male or female babies, eight of the women were told prenatally they were expecting a female when in fact the baby was male, and in five of the cases the women were told the fetus was a male when it was actually a female. This study has found that approximately 1 in 200 women will be told the wrong sex at their anomaly scan.
Reasons for wanting to know the sex of their baby
In this study the age, race, religion, parity and past history of fertility problems were assessed to see if they influenced the decision to know the fetal sex. The first and most significant factor was age. There was a strong association between being younger (< 30 years old) and having an increased desire to know the sex – (Figure 1). Over 90% of 15–20 year-olds wanted to know the sex of their baby, whereas for women over 41 only 55% requested the information. There is a clear pattern that shows with increasing age fewer women want to know the sex of their unborn child. In our study 81% of women under 30 years old wanted to know the sex of their baby compared with 64% of women over 30 years old (P < 0.001). Similarly, other studies have demonstrated that younger mothers preferred to know the sex.
3,14,15
However, for all age groups in the study over 50% did request sex determination.
Maternal age in relation to women wanting to know the sex of the fetus
We also wanted to assess whether parity influenced their choice. In our study there were a similar number of women having their first child (n = 1345) compared with multiparous women (n = 1435). It was found that 71% of the primigravida women wanted to know the sex compared with 77% of multiparous (P < 0.001). This suggests that multiparous women were significantly more likely to want to know. Other studies have suggested that it was more common for primigravida women to find out the sex than multiparous women, although this may be related to the cultural differences between Nigerian and British women. 14,17 Shipp et al suggested that if women obtained the information in their previous pregnancies they were more likely to want to know in subsequent pregnancies. 3
We then chose to combine age and parity of the women to see if this affected the decision. Figure 2 indicates that multiparous women in all age groups had a greater percentage wanting to find out the sex compared to those not wanting to know. There are a number of possible reasons why multiparous women are more likely to want to know the sex in view of the sex of their previous children, and their domestic and housing arrangements. Also future childbearing decisions may depend on the sex of the current pregnancy.
14
Maternal age and parity in relation to women wanting to know the sex of the fetus
We investigated whether maternal race influenced the decision to want to know. Figure 3 shows that most racial groups had a very similar percentage of women wanting to find out the sex, with a trend for white Caucasian and Asian women to be less likely to want to know the sex compared with Afro-Caribbean women. This was also suggested by Shipp et al.
3
However, it is notable that 100% of Chinese women (n = 39) wanted the information. We believe this may be related to the one child policy allowed in China.
Maternal race in relation to women wanting to know the sex of the fetus
On investigating religion, Figure 4 shows that all religions except Jewish women had a similar preference to know the sex of their unborn child including those with no religious beliefs. Only 32% of Jewish women requested to know the sex, which is significantly less than all other groups (P < 0.01). We believe this issue has not been reported in previous studies, and recommend further study in this area. However, it is important to acknowledge that although a patient may select a particular religion, this may not necessarily mean they follow its teachings.
Religious background in relation to women wanting to know the sex of the fetus
There has been a suggestion that fertility may influence a woman's choice. There were 167 women in the study who were identified as experiencing subfertility. This cohort was found by identifying women who had previously attended fertility services within SRFT Hospital. Therefore, this was somewhat limited as it did not include those who received care outside of the trust and also may have included women who had attended only one appointment. In addition the cohort only included the maternal fertility issues and not the paternal. We found that only 69% of these women wanted to know, compared with 75% of those who had no problem conceiving. This difference however was not statistically significant (P = 0.145). Finally, we compared age and past medical history of fertility problems. Of this group, older women were least likely to want to know the sex; over 50% of women aged 41–47 with a history of fertility problems did not want to know the sex.
Conclusion
In conclusion, the majority of women attending for their anomaly scan at Salford Royal Foundation Trust Hospital wanted to know the sex of their baby (74.2%). Of these 98.2% were able to be told the sex, and this was accurate in 99.4% of cases. In addition, our results suggest that younger and parous women were significantly more likely to request this information. Jewish women were significantly less likely to want to know. This large study has addressed the issue of sex determination and may encourage further research to clarify the accuracy of transabdominal ultrasound sex determination and decision making involved in fetal sex determination.
DECLARATIONS